JPS6326245Y2 - - Google Patents

Description

[Detailed description of the invention] This invention is based on the invention that when the front and rear wheel differential control means is not operating in the direction of blocking the differential function, when the deceleration of the vehicle exceeds a predetermined value, the front and rear wheel differential control means automatically activates the front and rear wheel differential control means. The present invention relates to a four-wheel drive vehicle that operates in the direction of inhibiting the differential function to improve braking performance when braking the vehicle.

In general, two-wheel drive vehicles have only two wheels that generate drive friction, so they have weak ability to climb hills, and if one of the two drive wheels gets into a muddy off-road (outside the road), the left and right wheels will be damaged. The differential device makes it impossible to generate any driving force, and furthermore, it has drawbacks such as the inability to overcome obstacles higher than the radius of the wheels. Four-wheel drive vehicles have been conventionally used to overcome the drawbacks of two-wheel drive vehicles. However, although four-wheel drive vehicles can solve the above drawbacks, as shown in Figure 1,
As the steering angle θ of the steering wheels increases and the difference in turning radius (R-r) between the front wheels and the rear wheels increases, the rotation speed of the front wheels (more precisely, the average rotation speed since the left and right wheels differ) and the rotation speed of the rear wheels increase. There is also a big difference in rotation speed. In this case, if you try to forcefully steer the vehicle, a very large torque will be generated at both ends of the propeller shaft and axle shaft that transmit rotation to the front and rear wheels, causing the steering wheel to become hard to respond to. This causes the front wheels and rear wheels to slip in opposite directions, causing a tendency for the vehicle to understeer (a phenomenon in which the turning radius is larger than the one that should be obtained due to the steering angle), and the vehicle's running is braked or stopped. , or a friction force (referred to as tight corner braking) is generated on the tires that causes the engine to stall. In order to solve this situation, there are four-wheel drive vehicles that are equipped with a front-rear wheel differential mechanism between the front wheels and the rear wheels. However, this time, if even one of the four front and rear wheels gets into the mud, the differential mechanism between the left and right wheels and the front and rear wheel differential mechanism work together, causing all or most of the wheels to get stuck in the mud. Driving force was supplied and the machine idled, causing the other 3
The drawback is that all wheels lose their driving force, making it difficult for the vehicle to move. To solve this situation, four-wheel drive vehicles equipped with front and rear differential mechanisms are equipped with front and rear differential control means (lock-up mechanism) that can control the differential function of the front and rear differential mechanisms. It is necessary to provide a non-slip differential mechanism). In other words, according to such a front and rear wheel differential control means, even if one of the front wheels and the rear wheels gets into mud, etc., it is possible to prevent the front wheel or the rear wheel from moving out of the mud by controlling the front and rear wheels in a direction that blocks the differential function of the front and rear wheel differential mechanism. It becomes possible to transmit the driving torque to the other wheel which has a high friction force. In addition, in a four-wheel drive vehicle equipped with such front and rear wheel differential control means, when the means is operating in the direction of blocking the differential function, the front wheels and rear wheels are integrated via the drive system. rotate. For this reason, when the vehicle suddenly brakes, either the front or rear wheels do not brake to a stop first, but the front and rear wheels can brake to a stop at the same time, which greatly improves the vehicle's braking performance. It has excellent characteristics.
As a four-wheel drive vehicle equipped with such a front and rear wheel differential mechanism and a front and rear wheel differential control means, for example,
There is something related to No. 57-114727.

However, in such four-wheel drive vehicles, the variation in deceleration during vehicle braking is unrelated to the operation of the front and rear wheel differential control means, so this means is not operated in the direction of inhibiting the differential function. There are cases where the vehicle is suddenly braked, and in that case, there is a problem in that the above-mentioned excellent braking characteristics of the vehicle cannot be utilized. Furthermore, it is difficult for the occupant to operate the front and rear wheel differential control means in the direction of inhibiting the differential function each time the vehicle is suddenly braked, resulting in a problem in terms of operability.

This invention was made by focusing on these conventional problems, and is a deceleration method for detecting vehicle deceleration in a four-wheel drive vehicle having a front and rear wheel differential mechanism and a front and rear wheel differential control means. A signal is input from the detection means and the deceleration detection means to control the front and rear wheel differential control means so as to operate the front and rear wheel differential control means in a direction to inhibit the differential function when the deceleration of the vehicle is greater than a predetermined value. It is an object of the present invention to solve the above problems by providing differential blocking means.

This invention will be explained below based on the drawings.

FIG. 2 is a diagram showing an embodiment of this invention. First, to explain the configuration, in Figure 2, 1
is a vehicle body, and 2 is an engine supported by this vehicle body 1. A transmission 3 and an auxiliary transmission 4 are connected to the engine 2. The transmission 3 has a high/low (two-speed) transmission that forms part of the sub-transmission 4.
A switching device 5 is connected to the high/low switching device 5, and a front and rear wheel differential mechanism 7, which also constitutes a part of the sub-transmission 4, is connected to the high/low switching device 5 via its output shaft 5a. The front and rear wheel differential mechanism 7 includes a differential case 7a, a pinion shaft 7b fixed to the differential case 7a, and two differential pinions 7c rotatably supported by the pinion shaft 7b. and two side gears 7d that are always in mesh with two differential pinions 7c. One end of a rear wheel propeller shaft 13 is connected to one side gear 7d, and a rear left and right wheel differential mechanism 14 is connected to the other end of the rear wheel propeller shaft 13. Left and right rear wheels 16a and 16b are connected to both sides of the rear left and right wheel differential mechanism 14 via rear wheel axle shafts 15a and 15b. 16b
It is designed to be able to absorb the difference in rotational speed. A first chain wheel 18 is connected to the other side gear 7d on the same axis, and the first chain wheel 18 is connected to a second chain wheel 20 via a chain belt 19. One end of a front wheel propeller shaft 21 is connected to the axle of the second chain wheel 20, and a front left and right wheel differential mechanism 22 is connected to the other end of the front wheel propeller shaft 21.
are connected. Left and right front wheels 25a, 25b are connected to both sides of the front left and right wheel differential mechanism 22 via front wheel axles 24a, 24b.
5b is designed to absorb the difference in rotational speed.
Differential case 7 of front and rear wheel differential mechanism 7
Front and rear wheel differential control means 26 is interposed between a and the first chain wheel 18. The front and rear wheel differential control means 26, as shown in FIG. A solenoid 23 that houses an iron core 23a on its axis that can move a lever spool 27a, and an oil chamber 29 that receives hydraulic pressure to operate the solenoid 23.
a has a hydraulic multi-plate clutch 29 connected to a port (inlet/outlet) of a front/rear wheel differential control valve 27; The hydraulic multi-plate clutch 29 includes a pair of clutch plates 29b and 29c, one of which is connected to the differential case 7d and the other to the first chain wheel 18. By adjusting the magnitude of the current flowing through the solenoid 23, the iron core 23a is moved, and as this iron core 23a moves, the spool 27a that it comes into contact with is moved, and the front and rear wheel differential control valves 2 are moved.
Adjust the oil flow in step 7. When a high hydraulic pressure is applied to the oil chamber 29a, the hydraulic multi-disc clutch 29 is frictionally engaged.
When the oil pressure in the oil chamber 29a is lowered, the hydraulic multi-plate clutch 29 slips, and when the oil chamber 29a is drained, the hydraulic multi-plate clutch 29 is disengaged from the frictional engagement. Reference numeral 28 denotes a steering means whose both ends are connected to front wheels 25a and 25b serving as steering wheels, and which is driven by a steering wheel (not shown). 31 is an oil chamber 29a of the hydraulic multi-plate clutch 29;
This is a front and rear wheel differential control detection means that measures the oil pressure of the front and rear wheel differential control means 26 to detect the operation of the front and rear wheel differential control means 26, that is, the presence or absence of frictional engagement of the hydraulic multi-plate clutch 29. 35 is a deceleration detection means (generally called a G sensor) that is placed on a part of the vehicle body 1 and detects the deceleration of the vehicle. 32 is an electronic control circuit that can input signals from the deceleration detection means 35 and the front and rear wheel differential control detection means 31 and output a signal to the solenoid 23 based on the signal results. This electronic control circuit 32 constitutes a part of differential blocking means that controls the front and rear wheel differential control means 26 to differentially move in the differential function blocking direction.

Next, the action will be explained. Currently, the vehicle is being operated without operating the front and rear wheel differential control means 26 in the differential prevention direction, and as shown in FIG. becomes larger, the front wheels 25a, 25b and the rear wheel 16
There is a large difference (R-r) in the turning radius (R, r) on the road surface between the front wheels 25 and 16b.
A large difference also occurs between the respective average rotational speeds of the rear wheels 16a, 16b and the rear wheels 16a, 16b. This difference in average rotational speed is absorbed by the operation of the front and rear wheel differential mechanism 7, and the vehicle can turn smoothly while being steered at a large steering angle θ. If the vehicle continues to run without the front and rear wheel differential control means 26 being operated in the differential prevention direction and the vehicle is suddenly braked for some reason, the deceleration of the vehicle will exceed a predetermined value. At this time, the deceleration detection means 35 detects that the deceleration of the vehicle has exceeded a predetermined value.
At the same time, the front and rear wheel differential control detection means 31 detects that the front and rear wheel differential control means 26 is not operating in the differential function inhibiting direction. Therefore, the detection signals outputted by the deceleration detection means 35 and the front and rear wheel differential control detection means 31 are transmitted to the electronic control circuit 3.
2, as shown in FIG. 4, the electronic control circuit 32 outputs a signal to the solenoid 23 to operate the front and rear wheel differential control means 26 in the direction of inhibiting the differential function. The current supply to the solenoid 23 gradually increases in response to a signal from the electronic control circuit 32, and as the spool 27a of the front and rear wheel differential control valve 27 moves downward in the figure, the oil pressure in the oil chamber 29a increases, causing the hydraulic multi-disc clutch 29 to generate friction. When engaged, the front and rear wheel differential control means 26 operates in the differential blocking direction, and the differential function of the front and rear wheel differential mechanism 7 is blocked. As a result, since the front wheels 25a, 25b and the rear wheels 16a, 16b rotate integrally via the drive system, when the vehicle suddenly brakes, one of the front wheels 25a, 25b and the rear wheels 16a, 16b rotates. wheels 25a, 25b, 16a, 1 without braking and stopping first.
6b all brake and stop at the same time, making it possible to exhibit extremely excellent braking performance. Furthermore, for the occupants, there is no need to operate the front and rear wheel differential control means 26 in the differential prevention direction every time the vehicle is suddenly braked, so the operability of the four-wheel drive vehicle can be improved. Furthermore, the above-mentioned braking is performed by detecting the deceleration of the vehicle.
Unlike the device described in the publication, this is not always done when the brake is stepped on. According to the device described in this publication, when the brake pedal is depressed, the
Braking is performed by wheel drive, and the frequency of four-wheel drive switching becomes extremely high.The frequent shocks generated during switching place a large burden on the driving staff, leading to decreased durability and driving feeling.

In contrast, in this embodiment, braking by four-wheel drive is performed only during sudden braking when the braking force of four-wheel drive is truly required, so the above-mentioned problem can be solved. Furthermore, even when the vehicle is turning, braking force can be applied by four-wheel drive only when braking force is truly needed, so tight corner braking can be appropriately avoided.

FIG. 5 shows another embodiment.

In addition to the deceleration detection means 35 and the front and rear wheel differential control detection means 31 provided in the previous embodiment, this embodiment also includes a friction coefficient detection means for detecting the friction coefficient between the tire of the wheel and the road surface. This is an additional feature. As the coefficient of friction between the tires and the road surface decreases, the braking friction force of the vehicle also decreases, resulting in poor braking efficiency. Therefore, when the coefficient of friction becomes low, the deceleration of the vehicle is set to a lower predetermined value accordingly, and when the deceleration exceeds the predetermined value, the front and rear wheel differential control means 26 is operated in the direction of inhibiting the differential function. I need to do it. In this way, the braking efficiency of the vehicle is improved. In FIG. 5, 30 indicates the vehicle body 1 near the steering means 28.
The steering angle detecting means is provided in the steering wheel and detects the state in which the steering means 28 moves to detect the steering angle of the steered wheels. Reference numeral 40 denotes a vehicle speed detection means that is provided in the vehicle body 1 near the output shaft 5a of the high/low switching device 5 and detects the rotational speed of the output shaft 5a to detect the speed of the vehicle. 41 is a front wheel 25a which is a steering wheel.
This vertical load detection means is provided on the vehicle body 1 near the front wheel 25a and roughly detects the force applied in the vertical direction to the contact surface between the tire of the front wheel 25a and the road surface. Reference numeral 42 denotes a steering force detection means that is provided as a part of the steering means 28 and detects a steering force generated by being driven by a steering wheel (not shown). 33
is a friction coefficient calculation device that receives signals from a steering angle detection means 30, a vehicle speed detection means 40, a vertical load detection means 41, and a steering force detection means 42, and calculates a friction coefficient between a tire and a road surface based on the signal results. It is. The reason why the friction coefficient can be calculated from these signal results is as follows. The formula for determining the moment M around the king pin axis when the vehicle is running is as shown below.

M=Nsinζ sinφe(r+Rwsinζ cosφe)+SRwsin
ζ sinφe cosζ +SXscosζ＋Nfrcosζ (Automotive Engineering Handbook, page 8-16, bottom right column,
(From the Society of Automotive Engineers of Japan) In this formula, M is the moment around the kingpin axis, so it is a value that can be found if the steering force is known, and N is the vertical load applied to the contact surface between the road surface and the tire of the steering wheel 25a, r is the scrub radius, Rw is the effective radius of the tire, and S is the force (side force) that acts in the horizontal direction perpendicular to the direction of travel of the tire at the contact surface between the road surface and the tire. This S is obtained from the formula S=Nfs (fs is the sideslip friction coefficient). Since this fs is a value that changes depending on the vehicle speed, S can be approximately estimated from the detection results of the vertical load detection means 41 and the vehicle speed detection means 40. Xs is expressed as Tsat/S, where Tsat is the self-aligning torque and is based on the vehicle type and steering wheel 2.
It is determined by the steering angle 5a. Therefore,
Xs can be roughly estimated if the vehicle type, steering angle, vehicle speed, and vertical load between the steered wheels and the road surface are determined. f is the coefficient of friction between the tires of the steering wheels 25a and the road surface. Further, ζ is an angle determined by the kingpin inclination angle δ and the caster angle β as shown in the following equation, that is, an angle that is naturally determined depending on the vehicle type.

tan ² ζ=tan ² δ+tan ² β φe is the steering angle of the steering wheel 25a. Therefore, M, N, φe, S, and Xs can be roughly estimated by detecting the steering force, the load applied in the vertical direction to the contact surface between the steering wheel 25a and the road surface, the steering angle of the steering wheel 25a, and the vehicle speed. , ζ, r, and Rw are determined by the vehicle type (specifications), and only f remains as an unknown quantity. Therefore, the friction coefficient calculating device 33 can roughly calculate the friction coefficient f when output signals of the detection values detected by the steering angle detection means 30, the vehicle speed detection means 40, the vertical load detection means 41, and the steering force detection means 42 are input. It is now possible to calculate with . Then, the calculation result is output to the electronic control circuit 32 as a signal. Therefore, the steering angle detection means 30, the vehicle speed detection means 40, the vertical load detection means 4
1 and the friction coefficient calculation device 33 collectively constitute a friction coefficient detection means. When a signal is input from the friction coefficient calculating device 33 to the electronic control circuit 32, the electronic control circuit 32 calculates and stores a predetermined value of vehicle deceleration according to the value of the friction coefficient. That is, when the coefficient of friction is a low value, the predetermined value of deceleration is also set low. Signals are input from the deceleration detection means 35 and the front and rear wheel differential control detection means 31 to the electronic control circuit 32, and when the deceleration of the vehicle exceeds the stored predetermined value and the front and rear wheel differential control means 26 is When the electronic control circuit 32 is not operating in the direction of inhibiting the differential function, the electronic control circuit 32 causes the front and rear wheel differential control means 26 to operate in the direction of inhibiting the differential function.
A signal is output to the solenoid 23 of the As described above, according to this embodiment, even when the coefficient of friction between the tires and the road surface is low, the braking efficiency of the vehicle can be improved and excellent braking performance can be exhibited.

As explained above, according to this idea,
A vehicle body, a front wheel and a rear wheel that are rotatably supported by the vehicle body, a front and rear wheel differential mechanism that is connected to the front and rear wheels and absorbs the difference in rotational speed between the front wheels and the rear wheels, and a front and rear wheel differential In a four-wheel drive vehicle having a front and rear wheel differential control means capable of limiting or blocking the operating function of a dynamic mechanism, a deceleration detection means for detecting deceleration of the vehicle and a signal input from the deceleration detection means are provided. and a differential blocking means that controls the front and rear wheel differential control means to operate the front and rear wheel differential control means in the differential function blocking direction when the deceleration of the vehicle is equal to or higher than a predetermined value. During sudden braking, all four wheels can be braked and stopped at the same time, resulting in excellent braking performance. In addition, for the occupants, there is no need to manually operate the front and rear wheel differential control means in the direction of blocking the differential every time the vehicle suddenly brakes, making it possible to improve the operability of four-wheel drive vehicles. Effects can be obtained. Furthermore, since braking force is applied by four-wheel drive only when braking force is truly needed, it is possible to improve durability and driving feel by reducing the load on the drive system, and to reduce the tight corner braking phenomenon. can be appropriately avoided.

Further, in other embodiments, it is possible to obtain an effect that excellent braking performance can be exhibited even when the coefficient of friction between the tire of the wheel and the road surface is a low value.

[Brief explanation of the drawing]

Figure 1 is a plan view of a vehicle showing the difference in the respective turning radii of the front wheels and rear wheels on a road surface when the steering angle of the steering wheel is large, and Figure 2 is a diagram of a four-wheel drive vehicle according to this invention. FIG. 3 is a partial cross-sectional schematic diagram showing the front and rear wheel differential control means, FIG. 4 is a block diagram showing the signal system of one embodiment shown in FIG. 2, and FIG. FIG. 6 is a schematic diagram of a four-wheel drive vehicle according to an embodiment, and FIG. 6 is a block diagram showing a signal system of another embodiment shown in FIG. 1... Vehicle body, 7... Front and rear wheel differential mechanism, 7a...
Differential case, 7b...Pinion shaft, 7c...Differential pinion,
7d... Side gear, 16a, 16b... Rear wheel, 23... Solenoid, 25a, 25b... Front wheel, 26... Front and rear wheel differential control means, 27... Front and rear wheel differential control valve, 29... Hydraulic pressure Multi-disc clutch, 30... Steering angle detection means, 31... Front and rear wheel differential control detection means, 32... Electronic control circuit (differential blocking means), 33... Friction coefficient calculation device, 35...
Deceleration detection means, 40...Vehicle speed detection means, 41...
... Vertical load detection means, 42 ... Steering force detection means.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) A vehicle body, a front wheel and a rear wheel that are rotatably supported by the vehicle body, and a vehicle that is connected to the front and rear wheels and absorbs the difference in rotational speed between the front wheels and the rear wheels. A deceleration detection means for detecting deceleration of a vehicle in a four-wheel drive vehicle having a front and rear wheel differential mechanism, and a front and rear wheel differential control means capable of limiting or blocking the differential function of the front and rear wheel differential mechanism. and a differential that controls the front and rear wheel differential control means so as to input a signal from the deceleration detection means and operate the front and rear wheel differential control means in the direction of blocking the differential function when the deceleration of the vehicle exceeds a predetermined value. A four-wheel drive vehicle comprising a blocking means. (2) The four-wheel drive vehicle is provided with a friction coefficient detection means for detecting a friction coefficient between the steered wheels and the road surface,
The differential blocking means inputs a signal from the friction coefficient detection means, and when the friction coefficient is a low value and the predetermined value of the deceleration is correspondingly low, the front and rear wheel differential control means is set in the differential function blocking direction. A four-wheel drive vehicle according to claim 1, characterized in that the four-wheel drive vehicle is controlled to operate.